Selective laser sintering (SLS) is well known in the art and has traditionally been employed to produce parts known as “rapid prototypes,” which are parts that are used to demonstrate a proof of concept or a requirement such as proper form and fit. The selective laser sintering process generally consists of producing parts in layers from a laser-fusible powder that is provided one layer at a time. The powder is fused, or sintered, by the application of laser energy that is directed to portions of the powder corresponding to the cross-section of the part. After sintering the powder in each layer, a successive layer of powder is applied and the process of sintering portions of the powder corresponding to the cross-section of the part is repeated, with sintered portions of successive layers fusing to sintered portions of previous layers until the part is complete. Accordingly, selective laser sintering is capable of producing parts having relatively complex geometries and acceptable dimensional accuracy from a variety of materials such as wax, plastics, metals, and ceramics.
Generally, SLS parts are produced directly from an engineering master definition in a computer aided design (CAD) model. The time required to produce a rapid prototype is therefore significantly shorter than with conventional methods such as sheet metal forming, machining, molding, or other methods commonly known in the art. Unfortunately, powder materials that have been used to date for selective laser sintering generally have relatively low mechanical properties due to the nature of the rapid prototype application. Accordingly, parts formed using selective laser sintering are typically not used within a production design or as production parts due to limited performance capabilities such as low or inconsistent mechanical properties.
Aerospace parts have relatively stringent design requirements compared with parts in other applications, primarily due to operating environments having extremely high loads and temperatures in addition to a relatively high amount of parts in a relatively small volume. For example, aerospace parts are commonly subjected to fluid exposure, pressure cycling, prolonged fatigue loads, buffeting, and a wide range of temperatures in operation, among others, and must further be as lightweight as possible to meet performance objectives. Additionally, aerospace parts such as ECS (environmental control system) ducts typically define relatively intricate shapes in order to route around other parts and aircraft systems within an aircraft. Moreover, aerospace structures must be capable of withstanding impact loads from maintenance, handling, and in the case of military aerospace structures, from threats such armor piercing incendiaries (API) or high explosive incendiaries (HEI). Accordingly, aerospace parts must be designed to accommodate a variety of operating environments and thus have design requirements that are beyond those of non-aerospace parts.